On Tuesday 26 June 2001 13:46, Ivan Powis wrote: > I have a MS K7T Pro2-A motherboard with VIA KT133 chipset > (VT82C686B bridge). Also with IBM DTLA307030 UDMA100 Drive. > > Originally I had SUSE 7.0 installed, which ran the disk as a > UDMA100 drive with reported (hdparm) transfer rates > 35 MB/s. > > Since my other systems run Mandrake I installed LM8 on this > system, but find that it won't recognise the drive as UDMA100, > and can't be made to with hdparm either. So it runs as UDMA33 > with transfer rates of 23 MB/s. For the specific application > intended for this system, thats a _significant_ performance > hit. > > Out of curiosity I installed the v2.2 kernel distributed with > LM8 and find that that is fine. So the I conclude the problem > is with the 2.4 kernel or at least the build distributed with > LM8. > > I've browsed a lot and find lots of stubs (rather than > concluded threads) about DMA100 and off-board controller > problems, but I haven't find anything definitive about the > onboard VIA, LM8 and v2.4. > > Is this a known problem? got a fix? > > I append edited versions of the v2.4 and v2.2 kernel dmesg log > and the output from "hdparm -i -Tt /dev/hda" under both > kernels > > v2.4: Well, you are (un)lucky to get that performance out of it. We have deliberately set kernel 2.4 to cripple itself when it sees a 686B southbridge. It is supposed to shut down DMA, and it does in most cases. When the problem with the 686B Southbridge has a stable workaround in the kernel (We cannot assume that all users will have access or will upgrade their BIOS to extinguish the _massive_corruption_ bug), then we will have a full-speed kernel for you. Until then, kernel-linus and 2.2 work. This bug has been observed in kernel 2.4, Win 95, 98 98SE ME NT and Win2K. It's symptoms are many and varied: Cannot write a full CD-R or CDRW. Resets itself on transfers of 100Mb or more Freezes during disk copy operations. It is a hardware bug in the chipset itself which we had no viable workaround for at production time (We knew of it just days before release. SuSE could not have known of it at all because their release was much earlier.) If you want the best performance from hdparm, you might want to go to /contribs and download drakopt. It works acceptably in most cases and finds right now the highest speed. A version scheduled for release in a few days will find the best speed/noise immunity tradeoff according to user-set standards. Civileme
